Retractor systems may be used in a variety of different surgical procedures to provide an opening through which the doctor may access the surgical site. In spinal surgeries, for example, a retractor system may be used to provide the surgeon with access to the patient's spine. The opening created by the retractor system may, for example, enable the doctor to insert surgical instruments into the body or enable visualization of the surgical site. One typical prior art retractor system includes a plurality of blades coupled to a retractor frame. In use, the blades may be inserted into an incision and then retracted to displace tissue surrounding the incision exposing the surgical site. To minimize trauma to the tissue, this tissue displacement should be refined and controlled. However, current retractor systems do not provide desired control of the distraction. More particularly, the devices currently in use are mechanically coupled so the surgeon has limited ability to feel the resistance at the blades or to rotate the blades affixed to the retractor arm independently. This limited control takes away the skilled surgeon's ability to finely adjust the movement of the retractor blades.
There has been considerable development of retractors and retractor systems that are adapted for use in less invasive procedures. Standard hand-held surgical retractors are well known in the prior art and can be modified to fit the contours of these small incisions. Typical retractors are also positioned into the soft tissue and are levered back to hold the wound open, frequently requiring re-positioning if they dislodge, obstruct the physician's view, or interfere with access to the surgical site. Minimally invasive surgical approaches are being applied to orthopedic spine surgery and more recently to spine surgery. Surgery on the spine involves multiple layers of soft tissue, bone, ligaments, and nerves.
In a typical spine fusion, at least two vertebral bodies are rigidly connected using screws implanted into the respective vertebral bodies with a solid metal rod spanning the distance between the screws. This procedure is not generally conducive to a minimally invasive approach. The insertion of pedicle or facet screws is relatively straightforward and can be accomplished through a minimal incision. The difficulty arises upon the introduction of a length of rod into a very small incision with extremely limited access and visibility. A single level fusion may require a 30-40 mm rod to be introduced into a 1 cm incision and a multilevel fusion may require a rod several inches long to fit into a 1 cm incision. For this reason, it is important that the minimal incision be maintained in an open and accessible condition for introduction of the rod.
Minimally invasive surgery offers significant advantages over conventional open surgery. First, the skin incision and subsequent scar are significantly smaller. By using more than one small incision rather than one large incision, the need for extensive tissue and muscle retraction may be greatly reduced. This leads to significantly reduced post-operative pain, a shorter hospital stay and a faster overall recovery.
Therefore, there is a need for improved methods and devices that can be used for retracting tissue to provide access to the surgical site while minimizing trauma to soft tissue surrounding an incision.